1. Field of the Invention
This invention relates to oral vaccines containing effective amounts of oocysts from cyst-forming protozoa for treating domesticated birds and to methods for using the oral vaccine for treating domesticated birds for diseases caused by cyst-forming protozoa.
2. Description of the Related Art
Avian coccidiosis is an intestinal disease primarily of poultry caused by protozoa in the genus Eimeria. Coccidiosis causes U.S. broiler producers an annual loss of over $ 350 million, with losses worldwide exceeding $ 1 billion. The disease has been controlled for decades by medication of feed with anti-coccidial drugs, but the appearance of drug-resistant strains of Eimeria and increased consumer pressure to reduce use of medicated feeds has prompted alternative control measures. Medication with several different anticoccidical drugs has been effective in preventing severe outbreaks of disease. However, the useful period of most of these drugs is limited because of the emergence of resistant strains of coccidia (Chapman, Vet. Parasitol., Volume 15, 11-27, 1984; Chapman, Res. Vet. Sci., Volume 38, 226-230, 1985; Jeffers, Avian Dis., Volume 18, 74-84, 1984; Long and Jeffers, Parasitol. Today, Volume 2, 236-238, 1986; Rose and Mockett, Paraite Immunol., Volume 5, 479-489, 1983). There has been success reported in preventing coccidiosis by immunizing chickens with nonviable extracts of infected tissues (McKenzie and Long, Poult. Sci, Volume 65, 892-897, 1986) and sporozoite antigen (Murray et al., In L. R. McDougald, L. P. Joyner, and P. L. Long (ed.), Research in avian coccidiosis. Proceeding of the Georgia Coccidiosis Conference 1985. University of Georgia Press, Athens, Ga., 1986). Although it is unclear what immune mechanism is responsible for establishing protection, it is known that both humoral (Danforth and Augustine, Poult. Sci, Volume 62, 2145-2151, 1988; Lillehoj and Ruff, Avian Dis., Volume 31, 112-119, 1987; Rose and Mockett, 1983, supra) and cell-mediated (Klesius and Hinds, Infect. Immun., Volume 26, 1111-1115, 1978; Lillehoj, Infect. Immun, Volume 55, 1616-1621, 1987; Morita et al., J. Psarasitol., Volume 59, 199-200, 1973; rose, Exp. Parasitol., Volume 42, 129-141, 1977; Rose and Hesketh, Infect. Imun, Volume 26, 630-637, 1979; Rose and Hesketh, J. Protozool., Volume 31, 549-553, 1984) immune responses are involved, with the latter playing a major role (Lillehoj, 1987; supra; Rose and Hesketh, 1979, supra; Rose et al., Parasite Immunol., Volume 19, 53-69, 1988).
One approach that has met with success is vaccination of day-old chicks with a mixture of low doses of virulent or attenuated Eimeria oocysts. Vaccination for coccidiosis is generally performed in the hatchery on the day of hatch by spraying live Eimeria vaccine directly onto the birds, or through injection directly into 18d embryos. The infective oocysts complete their life cycle inside the intestinal tract of the bird culminating with the release of a new generation of unsporulated oocysts in 5-11 days post-infection, the time-frame being dependent on the species of the Eimeria. The unsporulated oocysts excreted with the feces then become infective, i.e., sporulate, in the outside environment and reinfect susceptible birds through host ingestion. Depending on a number of factors (e.g. infection dose), the birds become immunized against coccidiosis. This immunity is characterized by a decrease and/or absence of parasites observed microscopically in the intestine, a reduction of the shedding of oocysts, a reduction of the intestinal lesions, a reduction of the clinical disease, and/or a reduction or prevention of weight loss. The acquired immunity wanes over a three to four month time period in the absence of subsequent exposure to infective oocysts.
Various types of vaccines and methods of vaccination are available for immunizing poultry against coccidiosis. Published U.S. Patent Application 2010/001518 A1, published Jan. 21, 2010 (Lang et al) teach a vaccine containing at least two different strains of a single species of a sporozoan Coccida genus. The publication discloses multivalent vaccines that comprise any and all Coccidia genuses. The publication teaches that the vaccine can be administered by any route including oral by eyedrop, intranasal, in feed, in water or by spray; in ovo, topically or by injection such as intravenous, subcutaneous, intramuscular, intraorbital, intraocular, intradermal, and/or intraperitoneal vaccine. The vaccine contains sporulated oocysts in potassium dichromate solution and diluted to the appropriate dose vaccine).
Patent application US2008/0190373, published Aug. 14, 2008 (Lee) teaches a method for spraying a soft gel form containing a therapeutic agent such as oocysts of Eimeria species as a plurality of beadlets that are sprayed directly onto chicks into a poultry hatchling tray containing hatchlings. The beadlets are consumed by the poultry hatchlings while in the hatchling tray. The publication discloses an edible temperature setting polysaccharide gel such as alginate or carrageenan powder is dissolved in water and contain an equal volume of a therapeutic agent such as an oocysts suspension. This gel composition is then placed in a dispensing apparatus and sprayed into the hatching trays. The spraying forms the beadlets. U.S. Pat. No. 7,354,593, issued Apr. 8, 2008 (McDougald et al.) discloses a vaccine for coccidiosis which contains a mixture of sporulated oocysts from precocious strains of E. acervulina, E. maxima, and E. tenella. The vaccine comprises sterilized oocysts suspended in a preservative consisting of phosphate buffered saline containing gentamicin, or in sterile distilled water containing a suspending agent such as gum, a cellulose derivative, a microcrystalline cellulose, carageenan, sodium alginate, pectin or starch, a polypeptide suspending agent such as gelatin; a synthetic polymer suspending agent such as polyacrylic acid or a silicate suspending agent such as magnesium aluminum silicate. These vaccines were administered by spraying the birds or by oral gavage.
U.S. Pat. No. 7,018,640, issued Mar. 28, 2006 (Evans et al.) discloses an in ovo vaccine for coccidiosis that included live Eimeria sporozoites or merozoites or a mixture of both in any physiologically suitable medium that is injected into the poultry egg during the final quarter of incubation.
U.S. Pat. No. 5,006,341, issued Apr. 9, 1991 (Davis et al.) discloses an oral vaccine that is a dry free flowing solid beadlet of a lipid-continuous emulsion containing about 25% to about 50% by weight water in a lipid such as hardened palm kernel oil and viable encysted protozoa such as a sporulated oocyst of a species of coccidium. The beadlet also includes a protective coating of animal feed, cement, and/or gypsum. The beadlets can be blended with feed ingredients to provide a composite feed formulation.
U.S. Pat. No. 5,068,104, issued Nov. 26, 1991 (Bhogal et al.) discloses an oral vaccine for coccidiosis which includes suspensions of excysted sporozoites in physiologically balanced medium containing water-soluble polymeric stabilizers such as gels, gelatins, polysaccharide gums, cellulose or cellulose derivatives which extend viability and storage. U.S. Pat. No. 4,552,759, issued Nov. 12, 1985 (Davis et al.) discloses a composition for control of coccidiosis where oocysts are added directly during the mixing of poultry feed or via a premix which is a solid free-flowing dry composition or it can be a paste or slurry with water for incorporation into poultry feedstuff by mixing or spraying.
While various vaccines and delivery systems have been developed for immunizing domesticated birds, there remains a need in the art for an effective vaccine and delivery system for the domesticated bird industry. The present invention described below includes a new delivery system for coccidiosis vaccines using gel bead technology that provides efficacious and safe vaccines which are different from related art vaccines and delivery systems.